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Showing papers on "Transient (oscillation) published in 1991"


Journal ArticleDOI
M. Klein1, G.J. Rogers1, P. Kundur1
TL;DR: In this article, a fundamental study of the nature of inter-area oscillations in power systems is presented and the effects of the system structure, generator modeling, excitation type, and system loads are discussed in detail.
Abstract: A fundamental study of the nature of inter-area oscillations in power systems is presented. The effects of the system structure, generator modeling, excitation type, and system loads are discussed in detail. Both small signal and transient stability analyses are used to determine the characteristics of the system. >

1,048 citations


Journal ArticleDOI
28 Sep 1991
TL;DR: In this paper, a direct induction machine torque control method based on predictive, deadbeat control of the torque and flux is presented, where the stator voltage required to cause the torque to be equal to their respective reference values is calculated.
Abstract: A direct induction machine torque control method based on predictive, deadbeat control of the torque and flux is presented. By estimating the synchronous speed and the voltage behind the transient reactance, the change in torque and flux over the switching period is calculated. The stator voltage required to cause the torque and flux to be equal to their respective reference values is calculated. Space vector PWM is used to define the inverter switching state. An alternative approach to deadbeat control for use in the transient or pulse-dropping mode is also presented. An alternative modulation scheme is presented in which transient performance is improved by specifying the inverter switching states and then calculating the required switched instants to maintain deadbeat control of the flux while reducing the torque error during the entire switching interval. A similar approach is used for a transient in the flux. The implementation of the control scheme using DSP-based hardware is described, with complete experimental results given. >

890 citations


Journal ArticleDOI
TL;DR: In this paper, the performance of multiphase machines designed for operation with static power converters is investigated, where the winding distributions are intentionally rectangular to better accommodate the rectangular waveforms of solid-state inverters.
Abstract: The performance of multiphase machines designed for operation with static power converters is investigated. The winding distributions are intentionally rectangular to better accommodate the rectangular waveforms of solid-state inverters. Equations which define the transient as well as steady-state behavior, including the computation of all machine inductances, are derived. In deriving these equations the space harmonics are specifically included. Equations for calculation of terminal voltages and electromagnetic torque are modified to account for nonsinusoidal air-gap-flux distributions. A conventional three-phase induction motor including the effect of space harmonics is simulated. >

265 citations


Journal ArticleDOI
TL;DR: To measure the characteristics of ultrasonic motors, such as the maximum torque, torque-speed relationship and the frictional coefficient at the contact surface, a method in which the torque is calculated from the transient responses is proposed.
Abstract: To measure the characteristics of ultrasonic motors, such as the maximum torque, torque-speed relationship and the frictional coefficient at the contact surface, a method in which the torque is calculated from the transient responses is proposed. The rise curve that is the transitional change in the rotor speed soon after turning on the motor gives the load characteristics, while the fall curve that is the decay of the rotor speed after turning off the motor yields the frictional coefficient of the contact surface. This method requires only a short time (the transient time of the motor) to complete the measurement. The relations between the transient responses, the load characteristics and the frictional force are analyzed, and the method is applied to a hybrid transducer type rotary motor and a traveling wave type linear motor. >

146 citations


Journal ArticleDOI
TL;DR: In this article, the performance of a thermal energy storage module is simulated numerically and the change of phase of the phase change material (PCM) and the transient forced convective heat transfer for the transfer fluid with low Prandtl numbers are solved simultaneously as a conjugate problem.

105 citations


Journal ArticleDOI
TL;DR: In this article, the transient response of a high-speed digital circuit is determined by the interaction of a lossy distributed transmission line network and lumped nonlinear circuits, and its implementation in an analog circuit simulator is discussed.
Abstract: The transient response of a high-speed digital circuit is determined by the interaction of a lossy distributed transmission line network and lumped nonlinear circuits. A robust and accurate method for the analysis of such a system is reported, and its implementation in an analog circuit simulator is discussed. The method uses a convolution technique and a time-domain impulse response to perform a transient simulation of a transmission line network. The time-domain impulse response is derived using a Fourier transform of modified frequency-domain scattering parameters. Implementation of the technique is verified by comparison with measured results. >

90 citations


Journal ArticleDOI
TL;DR: In this article, the transient behavior of a symmetrically loaded DFG after a three-phase short circuit is presented, where both speed and rotor excitation voltage and frequency remain unchanged during short circuit.
Abstract: The doubly fed induction generator (DFG) is a variable-speed constant-frequency generator operating in either subsynchronous or supersynchronous mode. The transient behavior of a symmetrically loaded DFG after a three-phase short circuit is presented. Both speed and rotor excitation voltage and frequency remain unchanged during short circuit. The complete mathematical model of the transient state and experimental results are given, along with the transient state equivalent circuit. >

89 citations






Journal ArticleDOI
F.-Y. Chang1
TL;DR: In this article, an efficient method for the transient simulation of nonuniform frequency-dependent transmission lines is presented, which consists of iterative waveform relaxation analyses of asymmetric disjoint two-port networks constructed with FFT waveform generators and characteristic impedances synthesized by applying the Gauss-Marquardt optimization technique.
Abstract: An efficient method for the transient simulation of nonuniform frequency-dependent transmission lines is presented. The method consists of iterative waveform relaxation analyses of asymmetric disjoint two-port networks constructed with FFT waveform generators and characteristic impedances synthesized by applying the Gauss-Marquardt optimization technique. The method can also be adapted for discrete-time analysis by replacing the FFT waveform generators with ideal transmission lines connected with waveshaping networks. Transient responses of uniform and nonuniform transmission lines with and without skin-effect parameters and terminated with linear and nonlinear loads are simulated for illustrations. The accuracy and efficiency of the relaxation technique are substantiated with exact analytical solutions and experimental data. >

Journal ArticleDOI
TL;DR: In this paper, the authors present both steady and transient analyses of the semi-empirical nonlinear differential equations which have been used to model the resonant rolling motions of two ships whose capsizes have been extensively discussed in the naval architecture literature.

Journal ArticleDOI
TL;DR: A simple model based on the time variation of an applied voltage and the internal electric field induced by the adsorbed electric charges on the cell substrate has been proposed and the results from the model agree reasonably well with the experimental observations.
Abstract: Transient currents induced by the polarity reversal of a dc voltage applied to a liquid-crystal cell have been experimentally studied. For voltages less than a characteristic value, the time occurrence of the peak current decreases with decreasing applied voltage, which is contrary to behavior expected for a normal carrier-transport process. To explain the experiments, a simple model based on the time variation of an applied voltage and the internal electric field induced by the adsorbed electric charges on the cell substrate has been proposed. The results from the model agree reasonably well with the experimental observations.

Journal ArticleDOI
01 Jan 1991
TL;DR: In this paper, the heating of heterogeneous materials by radio frequency excitation is modeled by sequential electromagnetic and thermal analysis using the finite-element method, and the results show good agreement with transient thermal measurements.
Abstract: The heating of heterogeneous materials by radio frequency excitation is modeled by sequential electromagnetic and thermal analysis using the finite-element method. The electromagnetic analysis comprises electrostatic modeling using temperature-dependent complex dielectric permittivity to account for the energy dissipating losses in the material. The thermal analysis consists of a transient finite-element procedure with temperature-dependent thermal and material properties. The results show good agreement with transient thermal measurements. >

Journal ArticleDOI
TL;DR: In this paper, measured electric and magnetic fields of switching transients are characterized in terms of their macroburst (series of transients) and micropulse (individual transient) properties and are classified according to substation voltage and type.
Abstract: Measured electric and magnetic fields of switching transients are characterized in terms of their macroburst (series of transients) and micropulse (individual transient) properties and are classified according to substation voltage and type. Transient fields typical for 115-500 kV air-insulated substations (AISs) and gas-insulated substations (GISs) are reported. Macrobursts of up to 10000 individual transients with varying amplitudes and pulse repetition frequencies of 40 kHz or more can be produced during a single switch. The highest amplitude micropulse field transients are shown to scale with substation voltage. Peak vertical electric fields of 16 kV/m and horizontal magnetic fields of 212 A/m have been measured on the ground under the bus in 500 kV AISs during disconnect switching. Peak field component amplitudes are shown to double at several meters above ground and to scale approximately as 1/r with distance from the bus. Electric field enhancement above a grounded structure to many times the normal free-space value was measured. The dominant frequencies of switching transients are between 0.5 MHz and 120 MHz, vary inversely with substation voltage, and are highest in GISs. >

Proceedings ArticleDOI
24 Jun 1991
TL;DR: In this article, two time-domain analysis methods for periodically switched systems, like converters, are presented, one analyzes the steady-state periodic behavior of the system, while the second describes the transient behavior.
Abstract: Two time-domain analysis methods for periodically switched systems, like converters, are presented. The first method analyzes the steady-state periodic behavior of the system, while the second describes the transient behavior. In contrast with state-space averaging, the methods do not use approximations, so exact results are obtained. The methods give more insight into the dynamical behavior of the system. This knowledge is useful in designing controllers. >

Patent
22 Jul 1991
TL;DR: In this article, a variable-frequency pulsewidth-modulated D-C to DC-to-D-C converter with zero-voltage switching is proposed to reduce transient turn-on losses.
Abstract: A variable-frequency pulse-width-modulated D-C to D-C converter allows operation at very high frequencies with minimal power transistor switch transient turn-on losses. A frequency control scheme is utilized wherein the controller of the converter causes switching to occur when the voltage across the power transistor switch is near zero volts. In addition to reducing transient turn-on losses, zero-voltage switching reduces noise generation in the circuit and simplifies the power transistor drive requirements. Other characteristics of opimal power transistor switch utilization are met in addition to turning the switch on under a zero potential. Maximum peak voltage across the switch is limited to approximately the ouput or input voltage level depending on the configuration used. In addition, peak and average currents through the switch are proportional to output power requirements and turn off transient dissipation is held to a minimum.

Journal ArticleDOI
TL;DR: In this article, a boundary element approach is used to solve inverse heat conduction problems in multidimensional and nonlinear situations, where discretized boundary integral equations are expressed and, to obtain satisfying results, are associated with regularization procedures over space and time (transient case).
Abstract: A boundary element approach is used to solve inverse heat conduction problems in multidimensional and nonlinear situations. In stationary and transient cases, discretized boundary integral equations are expressed and, to obtain satisfying results, are associated with regularization procedures over space and time (transient case). The efficiency of the method, which depends on the accuracy of the measurements, is explored through an example of transient bidimensional application. A comparison with the superposition method (linear problems) is presented.

Journal ArticleDOI
TL;DR: In this article, an error estimation technique for adaptive finite element analysis of heat conduction problems is described, and the performance of this technique is demonstrated using a two-dimensional steady-state linear benchmark problem with a known analytical solution.
Abstract: An error estimation technique for adaptive finite element analysis of heat conduction problems is described. The performance of this technique is demonstrated using a two-dimensional steady-state linear benchmark problem with a known analytical solution. A transient non-linear heat conduction problem involving solidification is then solved as a typical practical application. Some preliminary investigations for error indicators in flow problems are presented.

Patent
09 May 1991
TL;DR: In this paper, a device for protecting an integrated circuit from transient energy is disclosed, which provides an SCR having a reduced "snap-back" trigger voltage, which is similar to the one described in this paper.
Abstract: A device for protecting an integrated circuit from transient energy is disclosed. This device provides an SCR having a reduced "snap-back" trigger voltage.

Patent
19 Aug 1991
TL;DR: In this paper, the operation and functioning of various elements in a circuit breaker panel assembly are monitored and tested using a permanently installed or a portable test module that can be plugged into a plug-in jack on the housing of the circuit breaker.
Abstract: The operation and functioning of various elements in a circuit breaker panel assembly are monitored and tested using a permanently installed or a portable test module that can be plugged into a plug-in jack on the housing of the circuit breaker panel assembly. The test module includes readout elements, data recording elements as well as telemetry networks for relaying data to a central station where such data can be reduced, recorded and analyzed by experts. The circuit breaker panel can include a voltage surge and transient protection network. A method of monitoring and testing is also disclosed.


Journal ArticleDOI
TL;DR: In this paper, an apparatus for the quantitative experimental investigation of the transient EHL problem for both line and point contacts is described, which can produce many types of dynamic load applied to the EHL contact zone.

Journal ArticleDOI
TL;DR: In this article, a transient theory of a double basin solar still is presented and explicit expressions for the temperatures of various components of the proposed system and its efficiency are derived for the effect of water depth on the performance of the system.

PatentDOI
TL;DR: In this article, the phase offset technique was used to improve the transient behavior of a two-way loudspeaker system, which included a crossover circuit with high selectivity, amplitude and phase correction circuitry for separately correcting the amplitude response curves observed on-axis and at different vertical angles off-axis.
Abstract: A circuit for improving the transient behavior of a two-way loudspeaker system includes a crossover circuit with high selectivity, amplitude and phase correction circuitry for separately correcting the amplitude and phase responses of the high and low frequency drivers in their mounting environment, and correction circuitry for correcting the composite amplitude and phase response of the overall loudspeaker system after insertion of the crossover. A further phase offset technique and circuit provides for introducing frequency dependent phase shift in the loudspeaker system's high or low frequency channels for offsetting the phase responses of the high and low frequency drivers within the crossover frequency range. According to the phase offset technique of the invention, phase shift is added, preferably in the high frequency channel, until composite amplitude response curves observed on-axis and at different vertical angles off-axis are forced to be consistent. After consistency is achieved the deterioration of the amplitude response resulting from the phase offset is corrected to a flat response by means of a forced series amplitude correction circuit inserted before the crossover. The result is improved transient response off-axis as well as on-axis.

Journal ArticleDOI
R. Itoh1, K. Ishizaka1
01 May 1991
TL;DR: In this paper, a three-phase flyback AC-DC convertor with step-up and stepdown characteristics of output voltage is described, which has a near unity power factor.
Abstract: A three-phase flyback AC-DC convertor which has the step-up and step-down characteristics of output voltage, is described. The introduction of pulsewidth modulation makes it possible to obtain the sinusoidal supply currents with a near unity power factor. Three gate-turn-off thyristors provide the necessary control over the currents for unidirectional power flow. To improve upon the oscillatory transient operations, the tested system includes the digital PID controller using a microcomputer for output voltage regulations. The experimental results and state-space simulations confirm the usefulness of the presented convertor. >

Proceedings ArticleDOI
TL;DR: In this article, a physical arc model is used to compare test circuits with respect to the thermal and dielectric interrupting interval of SF/sub 6/ circuit breakers.
Abstract: The interrupting capability of SF/sub 6/ circuit breakers has increased drastically during the last decade. After the development tests, high-voltage circuit breakers are tested in the high-power laboratory, where test conditions prescribed by standards and switching conditions in electrical transmission networks are simulated. It is important that the test circuits used in the laboratory give a correct representation of the current and voltage stress. The equations and parameters of a physical arc model are presented which can be used to compare test circuits with respect to the thermal and dielectric interrupting interval of SF/sub 6/ circuit breakers. An example calculation with the alternative transient program (ATP) shows the interruption of a terminal fault with a 4-parameter TRV. The sensitivity of the arc model in the thermal interrupting interval is demonstrated by comparing artificial line circuits. >

Journal ArticleDOI
TL;DR: In this article, the transient performance of generator-driven and capacitor-driven induction-type coilguns is investigated, as a function of the dimensions, material properties, type of supply, firing sequence of switching elements, and connections of drive coils.
Abstract: Computer simulation is used to investigate the transient performance of induction-type coilguns as a function of the dimensions, material properties, type of supply, firing sequence of switching elements, and connections of drive coils. The performance of both generator-driven and capacitor-driven coilguns is addressed. It is shown that the generator-driven coilgun performs satisfactorily in the starting section. However, at high velocity, the transit time is close to the electrical transient time constant, and therefore the DC components produce a retarding force. To avoid this problem, the three phase voltages should not be switched on simultaneously, but rather phase-by-phase according to their zero current crossing points. This can also alleviate the problem in the transient between the sections. The capacitor-driven coilguns, instead, derive the alternating current needed to create a traveling wave from resonance with the inductance of the coils. Therefore, the initiation of the sinusoidal current oscillation coincides with the switch-on time. They are ideally suited for short-time, high-acceleration operation, but they are likely to require higher operating voltages than the generator-driven coilguns, because of the constraint imposed on the capacitance by the resonance condition with attenuation. >

Journal ArticleDOI
TL;DR: In this paper, the importance of frequency response considerations in the use of thin-film gages for unsteady heat transfer measurements in transient facilities is considered, and methods for evaluating it are proposed.